添加write batch事务的实现

andrewbytecoder · andrewbytecoder · commit 0efabfe1087e · 2023-12-08T18:46:35.000+08:00
diff --git a/demo/CMakeLists.txt b/demo/CMakeLists.txt
@@ -1,6 +1,5 @@
 cmake_minimum_required(VERSION 3.9)
 # Keep the version below in sync with the one in db.h
-project(leveldb VERSION 1.23.0 LANGUAGES C CXX)
 
 
 
@@ -19,4 +18,8 @@ target_link_libraries(test
         PUBLIC leveldb)
 
 target_include_directories(test
-        PUBLIC ${PROJECT_SOURCE_DIR}/../include)
+        PUBLIC ${PROJECT_SOURCE_DIR}/include)
+
+
+# 添加各个算法测试代码
+add_subdirectory(batch_test)
diff --git a/demo/batch_test/CMakeLists.txt b/demo/batch_test/CMakeLists.txt
@@ -0,0 +1,16 @@
+cmake_minimum_required(VERSION 3.9)
+# Keep the version below in sync with the one in db.h
+# 这里一旦指定project那么下面所有的 ${PROJECT_SOURCE_DIR} 都会变成当前目录
+#project(leveldb VERSION 1.23.0 LANGUAGES C CXX)
+
+
+add_executable(write_batch
+        write_batch_main.cpp
+        write_batch_demo.cpp)
+
+#target_link_libraries(test
+#        PUBLIC leveldb)
+
+target_include_directories(write_batch
+        PUBLIC ${PROJECT_SOURCE_DIR}/include)
+
diff --git a/demo/batch_test/write_batch_demo.cpp b/demo/batch_test/write_batch_demo.cpp
@@ -0,0 +1,5 @@
+//
+// Created by wangyz38535 on 2023/12/5.
+//
+
+#include "write_batch_demo.h"
diff --git a/demo/batch_test/write_batch_demo.h b/demo/batch_test/write_batch_demo.h
@@ -0,0 +1,79 @@
+//
+// Created by wangyz38535 on 2023/12/5.
+//
+
+#ifndef LEVELDB_WRITE_BATCH_DEMO_H
+#define LEVELDB_WRITE_BATCH_DEMO_H
+
+#include <algorithm>
+#include <string>
+#include "leveldb/slice.h"
+#include "leveldb/export.h"
+#include "leveldb/status.h"
+
+/*
+ * 对write_bach 进行重新实现，一般理解里面的实现原理
+ *
+ * */
+namespace WRITE_BATCH_DEMO {
+
+
+    class WriteBatch {
+    public:
+        class LEVELDB_EXPORT Handler {
+        public:
+            virtual ~Handler();
+
+            virtual void Put(const leveldb::Slice &key, const leveldb::Slice &value) = 0;
+
+            virtual void Delete(const leveldb::Slice &key) = 0;
+        };
+
+        WriteBatch();
+
+        // Intentionally copyable.
+        WriteBatch(const WriteBatch &) = default;
+
+        WriteBatch &operator=(const WriteBatch &) = default;
+
+        ~WriteBatch();
+
+        // Store the mapping "key->value" in the database.
+        void Put(const leveldb::Slice &key, const leveldb::Slice &value);
+
+        // If the database contains a mapping for "key", erase it.  Else do nothing.
+        void Delete(const leveldb::Slice &key);
+
+        // Clear all updates buffered in this batch.
+        void Clear();
+
+        // The size of the database changes caused by this batch.
+        //
+        // This number is tied to implementation details, and may change across
+        // releases. It is intended for LevelDB usage metrics.
+        size_t ApproximateSize() const;
+
+        // Copies the operations in "source" to this batch.
+        //
+        // This runs in O(source size) time. However, the constant factor is better
+        // than calling Iterate() over the source batch with a Handler that replicates
+        // the operations into this batch.
+        void Append(const WriteBatch &source);
+
+        // Support for iterating over the contents of a batch.
+        leveldb::Status Iterate(Handler *handler) const;
+
+    private:
+        friend class WriteBatchInternal;
+
+        std::string rep_;  // See comment in write_batch.cc for the format of rep_
+    };
+
+}
+
+class write_batch_demo {
+
+};
+
+
+#endif //LEVELDB_WRITE_BATCH_DEMO_H
diff --git a/demo/batch_test/write_batch_internal_demo.cpp b/demo/batch_test/write_batch_internal_demo.cpp
@@ -0,0 +1,5 @@
+//
+// Created by wangyz38535 on 2023/12/5.
+//
+
+#include "write_batch_internal_demo.h"
diff --git a/demo/batch_test/write_batch_internal_demo.h b/demo/batch_test/write_batch_internal_demo.h
@@ -0,0 +1,14 @@
+//
+// Created by wangyz38535 on 2023/12/5.
+//
+
+#ifndef LEVELDB_WRITE_BATCH_INTERNAL_DEMO_H
+#define LEVELDB_WRITE_BATCH_INTERNAL_DEMO_H
+
+
+class write_batch_internal_demo {
+
+};
+
+
+#endif //LEVELDB_WRITE_BATCH_INTERNAL_DEMO_H
diff --git a/demo/batch_test/write_batch_main.cpp b/demo/batch_test/write_batch_main.cpp
@@ -0,0 +1,16 @@
+//
+// Created by wangyz38535 on 2023/12/5.
+//
+#include <iostream>
+
+#include "write_batch_demo.h"
+
+
+int main(int argc, char **argv) {
+
+
+
+    return 0;
+}
+
+
diff --git a/demo/leveldb_exec.cpp b/demo/leveldb_exec.cpp
@@ -21,8 +21,10 @@ int main(int argc, char *argv[]) {
     // 数据库的读写
     std::string value = "value";
     std::string key1 = "key1";
+    leveldb::WriteOptions write_options;
+    write_options.sync = true;
 
-    auto s = db->Put(leveldb::WriteOptions(), key1, value);
+    auto s = db->Put(write_options, key1, value);
 
     for (int i = 0; i < 100; ++i) {
         std::string key = to_string(i);
diff --git a/demo/test.cpp b/demo/test.cpp
@@ -14,18 +14,37 @@
 #include <set>
 #include <iostream>
 #include <cassert>
+#include <functional>
 #include "leveldb/write_batch.h"
 #include "leveldb/db.h"
 
 using namespace std;
 
+template<int max>
+class A {
+
+private:
+    int m_a;
+};
+
+class B {
+public:
+
+
+private:
+    int m_b;
+};
+
 
-const uint64_t CREATE_SQL_STR_LEN = 1024 * 1024;
 
 int main(int argc, char *argv[]) {
 
-    int *lpData = nullptr;
-    std::cout << sizeof(*lpData) << std::endl;
+    const std::set<int32_t>  data1;
+    const std::set<int32_t>  &data = data1;
+
+
+
+    std::end(data);
 
 
     return 0;
diff --git a/doc/index.adoc b/doc/index.adoc
@@ -31,7 +31,9 @@ ____
 
 
 include::instruction/readme.adoc[readme]
+// impl中进行总体介绍，在后面跟着对应的实现
 include::instruction/impl.adoc[impl]
+include::instruction/write_batch_impl.adoc[write_batch_impl]
 
 include::persistence/log_format.adoc[log_format]
 
diff --git a/doc/instruction/impl.adoc b/doc/instruction/impl.adoc
@@ -26,3 +26,12 @@ endif::rootpath[]
 
 
 
+=== write batch
+levelDB虽然只是一个简单的键值对数据库，但是其中关于数据的处理特别是对slice的使用，简直是玩出花来了，非常值的参考，write batch的实现就是一个例子。
+
+
+
+
+
+
+
diff --git a/doc/instruction/readme.adoc b/doc/instruction/readme.adoc
@@ -208,29 +208,18 @@ if (s.ok()) {
 
 WriteBatch将一些列动作封装成一个原子操作，当需要对数据库进行多次修改时，可以将这些操作封装成一个batch，这样能有效加快这些更改。
 
-== Synchronous Writes
+== 同步写
 
-By default, each write to leveldb is asynchronous: it returns after pushing the
-write from the process into the operating system. The transfer from operating
-system memory to the underlying persistent storage happens asynchronously. The
-sync flag can be turned on for a particular write to make the write operation
-not return until the data being written has been pushed all the way to
-persistent storage. (On Posix systems, this is implemented by calling either
-`fsync(...)` or `fdatasync(...)` or `msync(..., MS_SYNC)` before the write
-operation returns.)
+每次levelDB的写操作其实都是异步的，当调用完系统接口之后接口就会返回，这时文件只是到系统内存并没有进行持久化，但是系统内存到真正的持久化之间是异步执行的。当需要接口同步写时可以将sync flag设置给put的WriteOptions，这样就能保证接口返回之前已经将值都写入到持久化文件里了。(在UNIX系统上是通过在写操作返回之前调用`fsync(...)` or `fdatasync(...)` or `msync(..., MS_SYNC)`等接口实现。)
 
-```c++
+[source,c++]
+----
 leveldb::WriteOptions write_options;
 write_options.sync = true;
 db->Put(write_options, ...);
-```
+----
 
-Asynchronous writes are often more than a thousand times as fast as synchronous
-writes. The downside of asynchronous writes is that a crash of the machine may
-cause the last few updates to be lost. Note that a crash of just the writing
-process (i.e., not a reboot) will not cause any loss since even when sync is
-false, an update is pushed from the process memory into the operating system
-before it is considered done.
+异步写的速度是同步写的千倍左右，异步写的问题就是系统崩溃时可能会丢失部分数据。
 
 Asynchronous writes can often be used safely. For example, when loading a large
 amount of data into the database you can handle lost updates by restarting the
diff --git a/doc/instruction/write_batch_impl.adoc b/doc/instruction/write_batch_impl.adoc
@@ -0,0 +1,25 @@
+:toc:
+
+:icons: font
+
+// 保证所有的目录层级都可以正常显示图片
+:path: instruction/
+:imagesdir: ../image/
+:srcdir: ../src
+
+
+// 只有book调用的时候才会走到这里
+ifdef::rootpath[]
+:imagesdir: {rootpath}{path}{imagesdir}
+:srcdir: {rootpath}../src/
+endif::rootpath[]
+
+ifndef::rootpath[]
+:rootpath: ../
+:srcdir: {rootpath}{path}../src/
+endif::rootpath[]
+
+
+== write batch
+
+
diff --git a/doc/persistence/log_format.adoc b/doc/persistence/log_format.adoc
@@ -101,3 +101,10 @@ bytes free in the third block, which will be left empty as the trailer.
 2. No compression.  Again, this could be fixed by adding new record types.
 
 
+
+
+
+
+
+
+

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +//
 +// Created by wangyz38535 on 2023/12/5.
 +//
++
 +#include "write_batch_demo.h"